Proceedings of the Royal Society: 267 
At this meeting the Lord Bishop of Limerick was admitted a 
Fellow of the society. 
Thursday, March 25. 
Major-General Sir John Malcolm, G.C.B., was admitted into 
the society. 
A Letter from the Rey. L. W. Dillwyn to Sir H. Davy, Bart. P.R.S, 
was read. 
This letter was supp/ementary to a former one, and contained 
further observations on the relative periods at which the different 
families of testaceous animals appear to have been created, and on 
the gradual approximation which may be observed in British 
strata, from the fossil remains of the oldest. formations to the living 
inhabitants of our present land and waters. 
The author observes that the dimyairia of the strata between the 
transition lime and lias have the ligament external, and that in- 
ternal ligaments were therefore confined to the monomyairia till 
after the deposition of the lias. 
In the beds above the lias, all the shells are referable to existing 
orders of animals, and it is only in the tertiary beds that any of 
the cirrhipeda, or families of the naked mollusca nave been found, 
What is generally considered as the beak of a sepia, Mr. Dill- 
wyn refers to the cephalopode animal of an ammonite. Every 
shell of the tertiary strata, the author observes, may be referred to 
some existing genus; but though this approximation has thus far 
proceeded in the London clay, yet its numerous species are now. 
extinct, and it is only in the upper beds of crag that any fossil can 
be completely identified with a living species. 
A letter from Mr, Tredgold to Dr. Thomas Young was also read, 
containing, 
An Account of his Experiments on the Elasticity and Strength of hard 
and soft Steel. 
The bars of steel used in these experiments were supported at 
the ends by two blocks of cast iron, resting upon a wooden frame, 
